When to (not) use normal maps
Not only do normal maps increase performance in games, but they also increase the speed and performance of renders. Normal maps are only supposed to be used for small details such as small dents, scratches, marks, etc. For small details, you should probably use a normal map.
However, normal maps do not modify the actual geometry of the object. They only change the direction light hits the mesh in certain areas, known as a normal (hence the name). To modify the geometry of a mesh with a texture, use a displacement texture.
So, for 3D printing, do not use a normal map as they only affect the shading of an object and not its geometry (3D printing only uses geometry for slicing the model). Use a displacement texture with the Displacement Modifier instead and apply it.